Upgrading coking coals and coke production

ABSTRACT

In coke production, coal fines are agglomerated by adding a liquid hydrocarbon to an aqueous dispersion of the fines and agitating the mixture to form spherical agglomerates. These agglomerates are separated, dried, preheated and carbonized.

ilnited States Patent Walsh et al.

[451 Jan. 25, 1972 UPGRADING COKING COALS AND COKE PRODUCTION Inventors:John H. Walsh, Manotick, Ontario; Basil J. P. Whalley, Ottawa, Ontario;John C. Botham, Ottawa, Ontario, all of Canada Canadian Patents andDevelopment Limited, Ottawa, Ontario, Canada Filed: Mar. 24, 1969App1.No.: 810,004

Assignee:

References Cited UNITED STATES PATENTS 6/1922 Trent ..209/49 1,838,88412/1931 Trent ..201/5 1,867,783 7/1932 Trent ..209/49 3,010,882 11/1961Barclay et a1. 201/6 UX 3,043,753 7/1962 Destremps et a1. .....20|/5 X3,117,918 1/1964 Batchelor et al..... 201/6 X 3,444,047 5/1969 Wilde..20 l /6 3,471,267 10/1969 Capes et al. ..23/313 FOREIGN PATENTS ORAPPLICATIONS 136,177 2/1950 Australia ..201/5 709,336 5/1965 CanadaPrimary Examiner-Norman Yudkoff Assistant ExaminerDavid EdwardsAttorney-Weir, Marshall, MacRae & Lamb [57] ABSTRACT In coke production,coal fines are agglomerated by adding a liquid hydrocarbon to an aqueousdispersion of the fines and agitating the mixture to form sphericalagglomerates. These agglomerates are separated, dried, preheated andcarbonized.

9 Claims, 1 Drawing Figure MINE-EAL [4*0 MESH COAL IN \VATEIZ 6U5PEN$IONEpAQATOIZ' 10-40 2 /w FlZOTl-l FLOTATION CELLO TAB FDINDEIZ/ 1AGlTATOlZ.

502551452); 3101 TYPE I -Dr2 5-2, QEHEA El? 1 7 p 1 Come Oven COKEHYDTZJOPHILlC MINERAL MATTER 4: \VATEEJ' UPGRADXNG COKING COALS AND COKEPRODUCTION The invention seeks to provide an effective and safepreheating process to produce coke of low sulphur and ash contents andto increase the output of conventional coke ovens.

In the production of coke in the conventional vertical slot coke oven,there are two well-recognized problems to which this invention seeks asolution, namely, (1) the difficulty in producing coke of desirably lowash and sulphur content, and (2) the difficulty in providing asatisfactory preheating step (a step which has productivity advantages)which can be conducted in an efiicient and safe manner.

With particular regard to the first problem, it will be recognized thatthe major problem in upgrading coal, as compared to other minerals, isthat in the latter case only a minor portion of raw substance to betreated is desired as end product; for coal, on the other hand, nearlyall the raw substance treated is desirable and the waste materialconstitutes only a minor fraction of the feed. It is evident then thatall so-called coal-clean-' ing procedures must recover a high proportionof raw coal to be economical. However, the present invention is of valuenot only for the treatment of raw coal but also in the recovery ofhigh-grade coal from the middle products obtained as a consequence ofconventional coal-cleaning operations. Physical separation processes canonly remove that proportion of sulphur held in association with thoseminerals distinct from the coal substance. Commonly, approximately 50percent of the sulphur content of coal will be held in this manner,normally in the form of the mineral, pyrite, or its immediate oxidationproducts. There is, however, another important consideration where thesulphur content of the coal is highly variable. Since coal was laid downunder geological conditions where considerable uniformity is to beexpected over large zones (indeed it is rare to find the coal substancevarying greatly in ultimate chemical composition in a coal seam althoughcoking properties may vary more widely in the same seam due to oxidationand other conditions that affect the reactive entities in the coalstructure) the variations found are generally less than the wide swingsin sulphur content reported in some commercially important coal seams.It is thought, therefore, that most of these swings in sulphur contentare caused by the presence or absence of the mineral pyrite which, insome cases, may have been introduced naturally in an erratic mannerduring the period of the geological formation of the coal bed. Thus, asuccessful manner of removing pyrite from coal would not only lower theoverall sulphur content of coal, but would also permit an importantimprovement in the reduction of variation of sulphur contents of coalproduced from some seams.

The most important application of coking coals is to produce coke foruse in the iron blast furnace process, in which a wide range ofiron-bearing materials are smelted with coke. It appears probable that,when smelting iron ore of low grade, the sulphur and slag-causingconstituents of coke are less important because these impurities can bemore easily handled in the large slag volumes produced from low-gradeore. Conversely, however, when rich iron ore burdens are used(frequently well prepared in a uniform physical condition whether ofsinter or of pellets), the lower impurity content results in low-slagvolume in the furnace which, in turn, makes it difficult to handle cokeshigh in ash and sulphur contents without the expensive alternative ofadding waste materials, such as gravel, to augment the quantity of slagproduced. This latter practice, however, has been necessary in someblast furnace plants. Furthermore, the tendency towards the use ofprepared iron ores has reduced the sulphur content of these ores to verylow levels by virtue of the oxidizing conditions prevalent in the orepretreatment processes. Sulphur-free natural gas may also be used as afuel injectant in the blast furnace process. In effect, therefore, whenthese conditions prevail, the only substantial quantity of sulphurentering the furnace enters with the coke.

Taking these factors into account, it is believed that a l percentreduction in the ash content of coke provides a benefit of from to 50cents per ton of iron and that a 0.1 percent reduction in the sulphurcontent provides a benefit of from 5 to 20 cents per ton of iron, overthe range of practices now current in the North American steel industry.

With regard to the second problem, while considerable attention has beengiven, particularly in Great Britain, to the modification ofconventional vertical slot coke ovens to permit higher temperaturehigher production operation (which would also allow the production ofcoke of lower sulphur content from coals of the same sulphur content) nopractical realization of this development has thus far been achieved.Preheating of the coal remains the one important possibility forindustrial development to obtain large increases in coke ovenproductivity (after exhausting the avenues presently being elaborated,notably the construction of high ovens to increase the batch size anduse of refractories of improved thermal conductivity).

The very high-unit capital cost of coke is becoming an importanteconomic problem in steel works. By preheating the coals to be coked inapparatus of reasonable capital cost and high efficiency, even when thepreheating temperature of the coal is limited to the range of 250350 C.,productivity advantages have been shown in both experimental andproduction scale ovens to amount to about 50 percent in favorable casesand about 40 percent in less favorable cases. There is little difficultywith the coking of preheated coals once the coals are charged into thecoke ovens. The quality of coke produced remains usually unchanged ormay even be improved when coals of weaker coking properties are used.The preheating technique has not yet been successfully realized on aproduction scale because of two major problems: (a) the lack of asatisfactory procedure for performing the heating, and (b) the lack of aprocedure for preheating and charging wherein safety from explosions canbe substantially assured.

The present invention seeks to provide a method of upgrading cokingcoals to lower ash and sulphur contents whereby the resulting coal isamenable to low cost, highly effective direct heating steps in theproduction of coke therefrom. More specifically, the inventioncontemplates the production of coal essentially free from fines as suchbut wherein the fines (from which explosions are normally initiated) arepresent as agglomerates with each individual particle therein coatedwith an oily material such as coke oven tar of characteristics chosen todecrease explosion hazards.

The invention will be described with reference to the accompanyingdrawing, the single figure of which is a flow sheet illustrating apreferred embodiment of the invention.

In accordance with the invention, coal fines are agglomerated intopellets of a size suitable for coke making. The coal fines, which willordinarily be of about 14 mesh (Tyler Standard), may be those normallyproduced in mechanical mining operations or those particularly ground toa size fine enough to liberate the mineral matter from the coal (inextreme cases as fine as 60 percent -325 mesh), and, if desired, blendedfor the purpose. The pellets will ordinarily by of l/ 16 to /4 inch insize but may be of larger size if required. In conventional coke makinga suitable pellet size range would be about percent /8 inch.

Another important aspect of this invention is the preblending of coalsof different ranks or types into the spherical agglomerates beforecharging to the coke oven. More intimate contact between the variouscoal constituents can be achieved in this way and this procedure caneither reduce the proportion of the generally more expensivelow-volatile coking coal required or can allow the use of a marginacoking coal otherwise difficult to incorporate into the oven coal blendwithout adversely affecting coke quality. It is also well known to theindustry that the addition of tar has a beneficial effect when somecoals are used, particularly those of low fluidity. This preblendingtechnique can also be used to incorporate inert additives such as cokebreeze, anthracite fines, petroleum coke, flue dust and other forms ofiron oxide to improve either the strength of the coke or lower its costdepending upon the particular circumstances at a given plant. Iron oxideadditions have generally not been favored because of the possible dangerof attack to the oven refractories (normally silica based).Incorporating the oxide inside the spherical agglomerates lessens thedanger of contact of the oxide directly with the oven walls.

The spherical agglomeration procedure generally comprises the dispersionof the coal fines in an aqueous phase, addition of a liquid hydrocarbonas a bridging liquid, and controlled agitation to cause coating of eachcoal particle with oil and pelletizing of the coated particles. Sincethe coal substance is naturally hyperophobic, essentially anyhydrocarbon liquid is suitable. But an important phase of the inventionresides in the use of tars and other hydrocarbon byproducts of cokingwhich are recovered on coking for recycling.

The oil-filled coal pellets are then separated as by screening from thewater and any other mineral matter or the like not attracted to the oilphase. The agglomeration procedure is closely similar to that describedin US. Pat. No. 3,268,071, Puddington et al.

The consistency of the aqueous dispersion, that is, the per centage ofsolids to water by weight, is about 10 to 40 percent. The hydrocarbonliquid is added in an amount of about 6 to 25 percent by weight ofsolids. Preferably, tl't: aqueous dispersion is maintained at atemperature of above 100 F. when undiluted viscous tar is used as thehydrocarbon liquid, or, alternatively, a light solvent (which may alsobe a byproduct of the coking step) can be added to the tar to lower theviscosity in proportions sufficient (generally ll5 percent by weight) toallow room temperature operation.

The mixing and agitation may be carried out in any suitable type ofapparatus; for instance, a drum equipped with a bladed propeller type ofmixer. Moreover, a specially developed apparatus in which a zone of highshear is produced in the annular space between a solid conically shapedvessel rapidly rotating inside another cone has been found to conditionrapidly the tar-coal-water mixture and also to serve as ablockage-resisting pump. After formation, the pellets are separated fromthe water phase, as by screening or by use of such size separators aselutriators, cyclones, or spirals, and dried, preferably by anair-drying procedure.

During the agitation, conditioning or balling steps, it has been founddesirable in some cases to add reagents to further the separation of thepyrite and mineral matter from the coal. In general, operating at abasicity (pH) of from 8 to 10 has enhanced separation and this can beachieved by lime additions. The use of depressants, such as cyanide ion,also aids in separation of pyrite. The presence of sodium silicate(which reagent can only be added after the preliminary balling step iswell underway as it inhibits ball formationat least with the Cape Bretoncoal studied), aids in the final agglomerate separation step when theelutriation process is used. The presence of bentonite is to be avoidedas it also inhibits ball formation in the case of the coals studied.

In industrial application of the process, the hot water needed whenundiluted coke oven tars are used as the bridging liquid, can beconveniently supplied from cooling water discharge of furnaces.Alternatively, surplus low-value steam can be condensed inside theballing tanks to supply both the makeup water and the heat requirement.

A direct relation has been found between the size of the agglomeratesproduced and the ratio of tar-to-coal used, and also with the time ofagitationin both cases increasing; with the first variable the mostimportant.

An important advantage of the present process is not only to prepare theupgraded coal into a size range amenable for treatment in efficientpreheating systems but also to produce the coal in a dewatered form. Itis well known that the addition of a hydrocarbon liquid to a wet coaldisplaces the water from the coal surface. This step occurs during thespherical agglomeration process and the small pellets produced willgenerally contain less than 5 percent water and frequently as low as 3percent provided steps are taken to avoid mechanical entrapment of wateron the pellets. This may be accomplished in vibrating screens and othershaking devices known to the industry but the application of a crudevacuum at this stage has been found especially helpful. In contrast,filter cakes of coal produced after the application of other separationprocesses that do not include the stage of agglomeration but using thesame feed coal size range, may contain as much as 20 percent water byweight. The economic advantage lies not only in the reduction of thermalenergy needed to remove the water but thermal drying processes arepotentially harmful to the quality of the coke produced due to thedanger of oxidation to fine coal. In the event that preheating practicescannot be used for other reasons, a significant improvement in coke ovenproductivity of the order of 20 percent may be expected on using theagglomerates directly as compared with the same coal at a typical ovencharge water content of 6 percent.

The hydrocarbon oil employed should be of low-sulphur content. Moreover,it is quite desirable, for economic reasons, that the oil be at leastpartially subject to reclaim for reuse in the agglomeration procedureand that any unreclaimed oil be otherwise usable. More specifically, ithas been found that coke oven tars and the like can be used underappropriate conditions to effect separation in the agglomerationprocedure set forth. It has been further found that at least onehalf ofthis added oil or tar can be recovered in the normal coking processbyproduct recovery system. The remainder of the tar not so recoveredappears as additional fixed carbon of coke and additional oilbyproducts.

Coal is difficult to preheat because of the fines contained, its watercontent, and its low-thermal conductivity. Moreover, the presence offine coal on heating leads to explosion hazards. The sphericalagglomeration process improves the porosity of coal beds to allow theinternal passage of heating gases. The danger of explosion is minimizedsince the individual coal particles are bound into the agglomerates. Itis inherent in the process that each particle of coal is coated with alayer of hydrocarbon. When the hydrocarbon is coke oven tar (in effectan already distilled liquid at a higher temperature than the preheatingprocess) which is placed on the surface of the coal particles, thelatter will only give up a minimum quantity of hydrocarbon to thepreheating gas. Moreover, the tar hardens on preheating, strengtheningthe agglomerates to allow their transport without undue breakdown andalso they become resistant to oxidation. This adds protection to the hotcoal awaiting oven charging not available in other processes.

Several types of preheating equipment can be used including moving beds,travelling grate machines, or fluid or spouting beds as circumstanceswarrant. Waste gases from various processes at a steel plant can be madeuse of in two different ways. In the first way, a gas of low-calorificvalue and low utility. Such as blast furnace gas (approx. B.t.u. per cu.ft.) can be precombusted and the resulting hot gaseous products passedthrough the preheating equipment. In the second way, gases alreadycontaining adequate sensible heat recovered from heating units, such asthe firing chambers of coke ovens or blast furnace stoves, can be passeddirectly through the preheater. For the case where a combustible gascontains suffi cient sensible heat to perform the coal preheating, thenthe hydrocarbon loss from the spherical agglomerates (at 300 C. about 3percent by weight) enriches this gas for use elsewhere, if attractive.Generally, a contact time of from 10 to 15 minutes is adequate for thepreheating step, and the temperature range used is 250 to 350 C.

A special case for carrying out the preheating step involves the use ofan autogenous heating device. The quantity of hydrocarbons released onheating the agglomerates to 300 C. (about 3 percent by weight) ifoxidized in situ in the preheating device is sufficient to provide thenecessary thermal requirement. A preferred type of preheater (because ofits inherently high capacity) has a hot zone at a temperaturesufficiently high to oxidize the evolved gases immediately on theirrelease and a time of passage of the spherical agglomerates such thattheir temperature does not exceed the desired level on traversing thishigh-temperature zone.

After preheating, the spherical agglomerates can be transported to, andcharged into, the coke ovens in conventional equipment. Pneumaticmethods of transport could also be used using a neutral carrier gas suchas steam at the temperature of the agglomerates. Alternatively,advantage can be taken of their substantially spherical shape to allowchutecharging techniques. When the entire oven charge is made up ofpreheated coal, a gain in output of 40 to 50 percent as compared tostandard wet coal charges will result.

Before the agglomeration stage, the coal fines suspension in the waterand oil may be upgraded by an optional air flotation step. This stepinvolves passing air bubbles upwardly through the suspension wherebysmall amounts of oil bridge the fines into larger particles of a sizesuitable for attachment to the rising air bubbles. After the aerationstep, the amount of hydrocarbon liquid may be adjusted, if necessary,and the concentrate subjected to controlled agitation to effectagglomeration. Again, reagents such as lime to control basicity andwellknown pyrite depressants may be used to aid mineral matterseparation.

The process can be combined integrally with other separating techniques(such as the water cyclone) to allow preliminary separation of a portionof the pyrite. Alternatively, the process can be fed with theintermediate products of other established separating techniques, suchas from jig or flotation circuits with or without preliminary sizereduction.

The flow sheet indicates diagrammatically a typical succession of methodsteps in accordance with the invention. The method illustrated includesan initial separation step followed by a flotation step. The upgradedcoal fines in aqueous suspension then pass into an agitator to which isfed a tar binder recovered from the subsequent preheating acarbonization steps. After the pelletizing step in the agitator, thecontents are screened to remove the pellets from the remaining aqueousliquid.

A series of tests have been carried out in order to illustrate theeffectiveness of the present invention. For the tests, there wereselected a high-sulphur coal which was obtained from No. 26 colliery,Harbour Seam, Cape Breton County, Nova Scotia, and a low-volatilereference coal obtained from Pocahontas No. 3 seam, Wyoming County, WestVirginia.

A typical analyses of these coals are,

TABLE I Bet. 1v No. 26 coal Classification:

Rank (ASTM) hv A b lvb Specific volatile index (unit basis). 169 209Volatile matter (dmmfb), percent. 35. 5 18. 7 Carbon (dmmib), percent87. 7 91. 3 Proxlmate analysis (db), percent:

Ash 6. 3 5. B 36. 9 18. 2 56. 8 76. 15, 350 15, 6'30 83. 6 85. 0 5. 3 4.5 1. 5 0. 74 1. 7 1. 2 Ash 3. 9 6. 1 Oxygen (by difi.) 4. 5 2. 4 Ashanalysis, percent:

Agglomerates were initially prepared from the No. 26 coal fines withparticles not substantially greater than 14; inch andat least percent ofwhich were l4 mesh (Tyler). The coal fines were dispersed in hot waterof about 70 C. in the proportion of about 20 percent. The bridgingliquid comprising a light coke oven tar was added to the dispersion inan amount of about 10 percent by weight of the coal.

The mixture was subjected to agitation in a 25-gallon drum stirred witha 9 inch diameter 3-bladed propeller, for about 60 minutes. Afterformation of the pellets they were separated from the water on a screenand air dried. The pellets used in the tests ranged in size from 1/16 to3/16 inch. The tar content ranged from 9.8 to 12.5 percent, and thewater content from 0.84 to 5.00 percent, the minimum consistent withsatisfactory balling being preferred for economic reasons.

Typical charges were prepared for carbonization using the sphericalagglomerated No. 26 coal fines, No. 26 coal crushed to about minus 5inch, and the low-volatile (1v) reference coal also crushed to aboutminus a inch.

The charges were carbonized in two types of apparatus (1) the UnitedStates Bureau of Mines-American Gas Association (BM/AGA) 18-inchdiameter retort and (2) the l2-inch Movable-Wall (MW) coke oven of theMines Branch, Department of Energy, Mines and Resources of Canada. Thelatter oven is 12 inches in width and has a 500 lb. (nominal) capacity.The walls comprise silicon carbide tile with a high thermal conductivityin relation to silica brick and to simulate the conditions of heating ina commercial oven the heat input is programmed. The coal is charged at aflue temperature of l,650 F. The temperature is then increased at a rateof 50 F./hr. to 1,950 F. and maintained at this temperature. The coke ispushed /2 hour after the center of coke has reached 1,850 F.

No attempt was made in these early tests to achieve mineral matter andpyrite rejection. The main objective was to prove the coking ability ofthe agglomerates and the degree of coke oven tar recycling that ispossible.

The results of the tests are given in tables l i, III, IV and V.

TABLE iIr-CARBONIZATION IN BM/AGA APPARATUS Coking temperature(average), F Coking time, hr Coal analysis (as carbonized) Sulphur Coalsize, x 0 1n Tar content of spher. aggl. percent Sieve analysis of coke(cumulative percent retained on):

4 1n. sieve 0.0 0.0 0.0 0. 0 3 n. sieve... 3. 2 1. 8 5. 9 4. 1 2 in.s1evo- 47. 1 37. 3 45. 3 38.1 1V in. sieve. 80. 1 76. 0 7T. 7 76. 6 1in. sieve. 94. 6 94. 8 92. 5 93. 8 in. sieve 96. 7 96. 6 95. 4 96. 0 3 5in. sieve 97. 3 97. 1 96. 5 96. 6 Coke size: Mean 2.00 1. 2. 00 1.91Tumbler test for coke (AST latlve ercentretained on):

Stab lity factor, 1 in. sieve 45. 7 48. 4 36.1 41. 5 Hardness factor, Min. sieve 67,1 66. 8 62. 9 60. 6 Apparent s ecltlc gravity, proximateanalysis 0 coke (dry), percent:

A511 7. 0 6. 7 8. 3 6. 5 1. 6 1. 4 2. 3 1. 1 91. 4 91. 9 89. 4 92. 4 Suihut in coke (dry)coke produced,

y eld, percent:

Coke: charge dry basis 71.1 70. 4 69.9 69. 4 Coke: coal dry basis 71. 173.0 69.9 74.1

1 Approximately. 1

TABLE Ill.--CARBONIZATION YIELDS (DRY BASIS) AND COKE QUALITY (BM/AGAAPPARATUS) 25% 1v coal 25% iv coal 37 No.26 50% No. 26 Description ofcharge 75% No. 26 336% No. 26 agg. 100% No. 26 50% No. 268th!- Iar foragglomerates, pound 0.0 5. 0.0 0. Yields:

Coke, percent:

Coke: charge 71. 1 70. 4 60. 0 on. X Coke: coal 71. 1 73. 0 60.0 74. 0Material balance, pound +3.0 +0. 4 Tor, gallon/ton:

Coke: charge 11.1 13.8 11.7 HA) Coke: coal 11.1 14.4 11.7 Materialbalance, pound +3. 5 +3. 1 Gas, cubic feet ton:

Coke: charge 10,470 10,200 11, 260 10, 000 Coke: coal 10, 470 10, 47711, 260 11. 400 Material balance, pound Light 011, gallon/ton:

Coke: charge 2. 2. 2 2. 4 Coke: coal 2. 2. 2 2. 6 Material balance,pound 0. 2. 2 +0. 2 Total material balance, pound 0.0 5. 0.0 +9. 7

TABLE IV.GAS ANALYSIS OF BM/AGA TESTS Test No 13 13-1 14 144 14-2 16 -117 17-1 Coal blend, percent:

LV ref. coal. 25.0 No. 26 coal... 37.5 100 50 No. 26 egg. coal 37.5 50(Percent by volume-air trecz) Carbon dioxide 0. 55 0.88 1 35 0. 55 0.140.89 0. 43 o. 27 0.07 Unsaturated hydrocarbons (illuminants) 3.58 4.53 1. 49 3. 5o 2. 42 4. 44 3. 30 4. 46 4.10 Hydrogen so. 97 57. 66 e3.65 59. 93 a5. 52 54. 65 57. 71 56.91 50. 33 Carbon monoxide. 5.10 4. 97'5. 25 6. 51 4. 63 0. 00 6. 17 6. 5.57 Paratiinic hydrocarbons 2s. 0427.15 24. 77 27. 66 22. 50 29. 23 25. c5 28. 63 25. 7a Nitrogen(difierence) 1. 76 4. 70 3.49 2. 75 4. 70 4. 70 6. 43 3. -20

TABLE E Q,% INES BRANCH MW COKE- The following is a comparison of thecoke strengths based upon the Stability Factor, ASTM Tumbler Test forCoke: Test No 334 340 357 Identification:

Coal blend, pcrlcent 25 0 40 TABLE VI Ref. lv coa NO- 26 C031 a 37- 5 50100 s m Facmr No. 26 coal (spher. aggl.) 37. 5 50 Ref. hv coal BM/AGA MWw i ii r i t) lb 497 a 49s 1 505 1 eg to clarge we Weight of charge(dry), 1b.. 485. 0 486. 2 494.0 25% 3g: l h I 6 Coal size, percent )6 x0 in 80 80 8O 25% Re 1V. P 88 Moisture, percent 2. 2. 4 2. 4 100% N0. 2636.0 Bulk density in oven (wet), lb./It. 50. 5 51. 5 100% when asst)41,5 40,7 Bulk density in 0(ven (C11')), 1? ./it. 1 8.54 142B; 1; Cokingtemperature average Coking timer t/ 10-20 10 30 Estimated value based onexperience with similar coals. Coal analyses (as carbonized) percent: 50Proxirnate analysis (db): 6 0 4 8 6 4tifi'a'saeriiiiiiiiiii::ijjjiijjjiijij: 31.5 3511 3115 There was noobserved significant difference in the Hardg ff Garbo" 3 1 2 ncssFactor. In general, the coke size was somewhat smaller Tar eont'entotspn eh 5555555551.- 10 5 10. 5 with the use of agglomerates. Thequality of the coke f f ggfg i (cumulative perm produced from the BM/AGAapparatus compared favorably 4 1... Sieve 2. a 4. 5 5. 5' with that fromthe MW coke oven.

g: 23 35% in general, there was no significant increase in the gas and i5 in. slev u so. 2 91. 6 92. 3 light oil yields; the composition of thegas also remained essen- ;;f;,3 g9? 3% tially the same. The tar used foragglomeration appeared to be i in: sleveII. 98.0 97. 7 97. 5 60recovered in the form of carbon in the coke and increased tar rii b lier t e s i ig r cil r e 's'iiiii (53.555555 551' 41 64 73 yields (about35-60 percent in coke and 65-40 percent in the cen retained tar). It ispostulated that this ratio would vary depending upon flit- 133, $512 $2}22;; the conditions of carbonization and the extent of gas cracking.Apparent specific gravity 886 89 86 While the thermal treatment of theBM/AGA tests indicates expansion 9 6 4 65 that a 40-65 percent makeup oftar may be required in an in- Final 2 6 6 4 -tegrated process, a tarbalance using 100 percent ag- 55239,,23, 1b 341 9 338, 5 34 G glomeratescontaining l0 percent added tar appears feasible. Yield. p f d b 1 71 769 8 70 5 As conventional coke oven practice would be carried out 1,172? f'fjfjjjjjjjjjijj 7 1 5 5 usually at a higher temperature, the tarrecovery in the fonn of coke analysis, perccnt 70 tar would be somewhatless than indicated above, while the mmlysls: x a yield of coke would behigher 5 \iolutllv 4 -{j The following conclusions may be drawn from thetests: iiii iiil uii ii 1,. E17 1.51.11: 1. Use of sphericalagglomerates in coal charges for coke 5 I l production resulted in cokewith better strength proper- Nl 75 ties (high-Stability Factor) and witha slightly lower rnean size, both in the case of a typical coke ovenchar and an hv coal charge. 2. Tar used for agglomeration is recoverablein the form of fixed carbon in the coke (35-60 percent and in the tarrecovery system (65-40 percent).

3. Gas yield and gas quality remain the same.

4. No change in light oil yield occurs.

5. From other results not reported here, the quality of the tar producedas measured by tests common in the industry was essentially unchanged.

In another example of this invention, run-of-oven feed sized coalnormally 80 percent less than 1% inch in size was agglomerated afternormal coal blending but without size reduction. In this case, afteraddition of the hydrocarbon bridging agent and agitating as before, onlythe fine fraction of the coal in the chargethat less than mesh insize-formed spherical agglomerates. All the coal was coated with thehydrocarbon whether agglomerated or not. The rejection of mineral matterand pyrite was restricted at best to that free from the coal matter atthe particular size distribution used. The mixture of agglomerates andlarge coal pieces was separated from the water slurry as before andbeing particulate with hydrocarbon coating was amenable to thepreheating techniques already described. This alternate procedure isused when the rejection of pyrite and mineral matter is secondary to thebenefit arising from preheating and has the advantage over the previousprocedure in that less hydrocarbon is needed to convert the coal into aform suitable for preheating, i.e., 3 to 10 percent of the weight of thecoal, depending upon the size range.

Another example of this invention is to produce a desirable feed forso-called form coke processes. In this latter type of coking process thecoal is preformed frequently by briquetting or extrusion methods andthen coked. The spherical agglomeration process produces an intimatelyblended feed containing tar of low mineral and pyrite content. In somecases the spherical agglomerates can be fed directly to a briquettingpress. Where hot briquetting techniques are preferred, the sphericalagglomeration product and procedure once again lends itself topreheating procedures but to the higher temperatures required (350-700C.) for the hot briquetting technique. Again, an important disadvantageof hot briquetting processes in the past was that hard to control fluidbed preheating steps were used with the possibility of oxidation of thecoking coal. The briquettes whether produced hot or cold can then be fedto the vertical shaft carbonization process.

We claim:

1. Process for producing coke which comprises dispersing a body of coalfines in water to form an aqueous dispersion of said coal fines, addinga bridging liquid consisting essentially of a coke oven tar to saiddispersion, said water in said dispersion being sufficiently hot torender said coke oven tar liquid, displacing the water on the individualfines of said body with said coke oven tar by agitating the resultingmixture of said dispersion and bridging liquid thereby to coat each saidindividual fine of said body with said coke oven tar, formingsubstantially spherical agglomerates of said coated fines by continuingsaid agitation of said mixture while avoiding mechanical entrapment ofwater in said agglomerates, separating said agglomerates from the waterin said mixture, drying said agglomerates, preheating said driedagglomerates in a preheating device to a temperature within the range ofa about 250 to about 350 C. by burning in situ combustible gasesincluding those arising on heating said agglomerates to said temperaturerange, transporting the preheated agglomerates from said preheatingdevice and charging said preheated agglomerates into a separate cokeoven, and carbonizing said agglomerates in said coke oven to fonn coke.

2. Process for producing coke as defined in claim 1, wherein saidbridging liquid is added in an amount of 6 to 20 percent based upon theweight of said coal fines.

3. Process for producing coke as defined in claim 1, wherein saiddispersion contains about 10 to 40 percent by weight of said coal fines.

4. Process for producing coke as defined in claim 1, including the stepprior to said agitation step, of aerating said mixture to form risingair bubbles therein and cause bridging of said fines into largerparticles suitable for attachment to said bubbles and removing sediment.

5. Process for producing coke as defined in claim 1, including the stepof forming a blend of said dried agglomerates and particles of naturalcoal and then carbonizingsaid blend.

6. Process for producing coke as defined in claim 1, including the stepsof controlling the basicity of said mixture in the pH range of 8-10 andadding a pyrite depressant to said mixture to aid in separationtherefrom of pyrite and other mineral matter.

7. Process for producing coke as defined in claim 1, wherein the saidpreheating step is performed by direct contact of combustible gasescontaining sufficient sensible heat, and wherein the hydrocarbon lossfrom said agglomerates during said preheating step is transferred tosaid gases for enrichment thereof and subsequent recycling.

8. Process for producing coke as defined in claim 1, including the stepof adding to said coal fines iron oxide-containing materials.

9. Process for producing coke which comprises agglomerating coal finesby preparing an aqueous dispersion thereof, adding a bridging liquidconsisting essentially of a coke oven tar to said dispersion, said waterin said dispersion being sufficiently hot to render said coke oven tarliquid, and agitating the resulting mixture to cause substantialdisplacement of the water on said particles by said bridging liquid andto form substantially spherical agglomerates of said fines containingsaid coke oven tar, separating said agglomerates from the aqueous phaseof said mixture, drying said agglomerates, preheating said agglomeratesto a temperature within the range of 350 to 700 C. by burning in situcombustible gases including those arising on heating said agglomeratesto said temperature range, briquetting said preheated agglomerates andcarbonizing said briquetted agglomerates to produce form coke.

I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,637,464 Dated January 25, 1972 Invmnmr(s) John H. Walsh, Basil J.P.Whalley, John E. Botham and Syed M. Ahmed It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

In the heading on the first page of the patent under [72],

the name of the fourth invention should be added as follows:

Syed M. Ahmed, Ottawa, Ontario-- Signes and sealed this 15th day ofAugust 1972.

(SEAL) Attest:

EDWARD M. FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. Process for producing coke as defined in claim 1, wherein saidbridging liquid is added in an amount of 6 to 20 percent based upon theweight of said coal fines.
 3. Process for producing coke as defined inclaim 1, wherein said dispersion contains about 10 to 40 percent byweight of said coal fines.
 4. Process for producing coke as defined inclaim 1, including the step prior to said agitation step, of aeratingsaid mixture to form rising air bubbles therein and cause bridging ofsaid fines into larger particles suitable for attachment to said bubblesand removing sediment.
 5. Process for producing coke as defined in claim1, including the step of forming a blend of said dried agglomerates andparticles of natural coal and then carbonizing said blend.
 6. Processfor producing coke as defined in claim 1, including the steps ofcontrolling the basicity of said mixture in the pH range of 8-10 andadding a pyrite depressant to said mixture to aid in separationtherefrom of pyrite and other mineral matter.
 7. Process for producingcoke as defined in claim 1, wherein the said preheating step isperformed by direct contact of combustible gases containing sufficientsensible heat, and wherein the hydrocarbon loss from said agglomeratesduring said preheating step is transferred to said gases for enrichmentthereof and subsequent recycling.
 8. Process for producing coke asdefined in claim 1, including the step of adding to said coal fines ironoxide-containing materials.
 9. Process for producing coke whichcomprises agglomerating coal fines by preparing an aqueous dispersionthereof, adding a bridging liquid consisting essentially of a coke oventar to said dispersion, said water in said dispersion being sufficientlyhot to render said coke oven tar liquid, and agitating the resultingmixture to cause substantial displacement of the water on said particlesby said bridging liquid and to form substantially spherical agglomeratesof said fines containing said coke oven tar, separating saidagglomerates from the aqueous phase of said mixturE, drying saidagglomerates, preheating said agglomerates to a temperature within therange of 350* to 700* C. by burning in situ combustible gases includingthose arising on heating said agglomerates to said temperature range,briquetting said preheated agglomerates and carbonizing said briquettedagglomerates to produce form coke.